Hi there, first post here. I couldn't find any threads with scenarios quite like this. Some were close, but here's my exact dilemma/question:

I have a mid-2009 MacBook Pro (5,5) with previous installs of OS X 10.6.8, Windows 7 64-bit, and Xubuntu 11.10 32-bit, using rEFIt as the bootloader. I was looking to try Linux Mint without replacing Xubuntu, and felt mint4win would be perfect. My question is if mint4win will, in a scenario such as mine, potentially be harmful to my already existent setup, or solely affect the Windows boot sector in a safe way. I don't know if I'm phrasing this correctly but what I'd like to see in an ideal world is me pressing the power button on my laptop, choosing the Windows option at the rEFIt boot menu, and then seeing the option to boot into Windows 7 or Mint. I'm pretty sure that would entail a second instance of GRUB existing on my machine though (aside from the one Xubuntu is using) and I'm really not sure if that's even possible. I suppose I could always use a VM when push comes to shove but I like the idea of mint4win better if it's possible and is safe.

It'd probably be better to use a VM instead. This way you can avoid any possible problems with your other three installations. I'm not sure how many bootable partitions you can have, but it seems to me as if you're pretty close to that limit. On top of that, you don't want to risk making the other operating systems unbootable.

You might be able to try installing Mint on a USB drive though and boot from that.